in reply to @ellie's post:
thanks for the nerdsnipe, doing this on my phone in a train with nano via ssh is something i dont recommend but heres an example of a js canvas in a svg: https://0x0a.de/cohostfun/train.svg
Re: "It gets grumpy if your code (or ink) has HTML characters, though. So you have to convert those, which is a pain. "
CDATA regions, as used in https://staging.cohostcdn.org/attachment/4ee00336-42a5-48be-bda8-f73d07e5c5ab/foo.svg